<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>自动生成字符串</title>
    <script>
        var num = prompt('请输入星星的个数');
        var str = '';
        for(var i = 1; i <= num ;i++){
            str = str + '★';
        }
        console.log(str);
    </script>
</head>
<body>

</body>
</html>